Analysis and prediction of copper surface roughness obtained by selective laser melting

The paper presents the results of experimental studies of the effect of mechanoactivation of the powder, argon shielding gas and the effect of technological modes of melting: the speed of the laser beam, the power of laser radiation, the scanning step, the preliminary temperature of heating the powder material on the surface roughness of the copper powder material obtained by selective laser melting. Experiments on the melting of copper powder are implemented on the installation of layer-by-layer laser melting of the original design, which allows to adjust all technological modes of melting. The surface roughness is determined on the non-contact digital microscope Olympus LEXT OLS4100. The mathematical dependence of the surface layer roughness of copper powder on the technological modes of melting is obtained on the basis of the theory of experiment planning and static processing of the results. The significant parameters of the regime-the power of laser radiation, the speed of the laser beam, the scanning step affecting the roughness of the layer. The positive effect of mechanical activation of powder material and protective atmosphere on the quality of the surface layer is shown

Система управления вторичным источником постоянного напряжения в системе автономного электропитания

Объектом исследования является повышающий преобразователь напряжения, входящий в состав зарядного устройства аккумуляторной батареи автомобиля. В процессе исследования проводился расчет элементов повышающего преобразователя, выбор аккумуляторной батареи, выбор солнечной панели. Были выбраны средства защиты зарядного устройства. Исследована работа ППН. Произведено имитационное моделирование работы повышающего преобразователя как с обратной связью так и без неё в программе LTspice. Был написан программный код системы управления преобразователем, генерирующий ШИМ сигнал, формируемый по уровню напряжения обратной связи.The subject of the study is an increase in the voltage converter that is part of the battery charger of the car. The research process included the calculation of elements of the step-up converter, the selection of a battery, and the selection of a solar panel. You have chosen to protect your charger. The work of par. A simulation simulation of the work of the step-up converter has been performed, both with and without the feedback in the LTSpice program. You have written the code for the converter control system that generates the PWM signal that is generated by the voltage level of the feedback

Analysis of molecular structures by homo- and hetero-nuclear J-coupled NMR in ultra-low field

The drawback of nuclear magnetic resonance (NMR) spectroscopy at ultra-low magnetic fields appears to be the lack of access to chemical information in terms of chemical shifts and homo-nuclear J-couplings. Here we report that a chemical group can be identified by the multiplet structure of the NMR spectrum in ultra-low fields if the condition of the strong hetero-nuclear J-coupling is fulfilled. Moreover we found that high-resolution ultra-low field proton-NMR spectra of liquids indeed reveal all hetero- and homo-nuclear J-couplings in terms of pairs of multiplets. This opens the door for the study of molecular structures at ultra-low magnetic fields. (c) 2007 Elsevier B.V. All rights reserved